Physical review. B./Physical review. B
Excited-state lifetime of the NV− infrared transition in diamond
Ronald Ulbricht, Zhi-Heng Loh
Abstract
The negatively charged nitrogen vacancy ($\mathrm{N}{\mathrm{V}}^{\ensuremath{-}}$) defect in diamond serves as a popular platform for manipulating and exploiting long-lived coherent spin dynamics at room temperature combined with optical readout. The required spin polarization of the spin triplet $^{3}A_{2}$ electronic ground state occurs through a cycle of repetitious optical photoexcitation events to the $^{3}E$ electronic excited state that is accompanied by a series of electronic transitions to a $^{1}A_{1}$ and a $^{1}E$ electronic state, and back to the $^{3}A_{2}$ state. The timescales of these transitions are largely known, yet for the relaxation time of the $^{1}A_{1}\ensuremath{\rightarrow}^{1}E$ infrared transition, which predominantly occurs via nonradiative recombination, only an upper limit of 1 ns could be determined so far. Here, we employ ultrafast transient absorption spectroscopy to probe the dynamics of the nonradiative relaxation from the $^{1}A_{1}$ to the $^{1}E$ state after photoexcitation of the $^{3}E$ state and find a relaxation time of 100 ps at a temperature of 78 K.